Cause and mechanism of liquid sheet breakup

Determine the exact physical cause and mechanism of liquid sheet breakup during the late stage of droplet aerobreakup in high-speed airflow, specifically identifying the conditions that trigger local thickness reduction and the onset of bi-axial extensional flow within the sheet.

Background

In the experiments, liquid sheets and ligaments form during the shear-induced entrainment (SIE) and catastrophic breakup modes of droplet aerobreakup. For Newtonian liquids these structures fragment into daughter droplets, whereas in viscoelastic liquids elasticity resists fragmentation, producing markedly different final morphologies.

The authors note that while it is qualitatively understood that local thinning and bi-axial extensional flow occur near rupture sites—processes that can stretch long-chain polymer molecules and generate large elastic stresses—the exact cause and mechanism driving the initiation of liquid sheet breakup remain unknown, motivating a precise physical characterization of the rupture process.